The present invention relates to a data processor, and more particularly, to a data processor that adds an error detection code and an error correction code to data provided from a host computer or performs an error correction process and an error detection process on data read from an optical disc medium to decode the data.
An optical disc device records data on an optical disc, which serves as a recording medium. For example, a CD-R/CD-RW system (optical disc device) that uses a CD-recordable (CD-R) disc, in which data is writable only once, or a CD-Rewritable (CD-RW) disc, in which data is rewritable, is widely used. To record data, the CD-R/CD-RW system encodes the data that is to be recorded by adding an error detection code (EDC) and an error correction code (ECC).
FIG. 1 is a block diagram schematically illustrating the configuration of a prior art CD-R/CD-RW system 50. The CD-R/CD-RW system 50 includes a CD-ROM encoder 1, a digital signal processing circuit 2, an analog signal processing circuit 3, a pickup 4, a pickup controller 6, a buffer RAM 7, and a control microcomputer 8.
The CD-ROM encoder 1 fetches 2048 bytes of data transferred from a host computer and encodes the data by adding an error detection code (EDC) and an error correction code (ECC) to the data. The encoding generates a block of CD-ROM data.
A block of CD-ROM data includes 2352 bytes (24 bytes×98 frames) of data. For example, when in mode 1, as shown in FIG. 2, each block includes 12 bytes of synchronization data, 4 bytes of header data, 2048 bytes of user data, 4 bytes of an error detection code EDC, 8 empty bytes, and 276 bytes of an error correction code ECC. Excluding the synchronization data, a scrambling process is performed on 2340 bytes of the block.
Nowadays, the CD-ROM encoder 1 is also used as a CD-ROM decoder, which decodes the CD-ROM data read from an optical disc by performing an error correction process and an error detection process on the CD-ROM data. In other words, the functions of an encoder and decoder are integrated into an integrated circuit.
A digital signal processing circuit 2 retrieves the CD-ROM data provided from the CD-ROM decoder in units of single frames (24 bytes). Then, the digital signal processing circuit 2 performs a predetermined operation on the data of a single frame in accordance with a cross-interleaved Reed-Solomon code (CIRC) to generate C1 and C2 codes. The digital signal processing circuit 2 adds the generated C1 and C2 codes to the data retrieved from the CD-ROM encoder 1 to generate 32 bytes of data. Further, the digital signal processing circuit 2 performs an interleaving process and then eight to fourteen modulation on the 32 bytes of data.
The analog signal processing circuit 3 receives the EFM modulated data in a serial state from the digital signal processing circuit 2, reads fluctuations in the level of the received data, and generates a laser control signal to control the radiation of a laser beam to the optical disc 5.
The pickup 4 radiates a laser beam on the optical disc 5 in accordance with the laser control signal and records the desired CD-ROM data on the optical disc 5. The optical disc 5 is, for example, a CD-R disc having a recording film in which data is writeable only once or a CD-RW disc having a recording film in which data is rewritable. In the CD-R disc, the recording film, which is formed from organic pigments, is melted by the heat of a high power laser beam. This forms pits for recording data. In the CD-RW disc, the recording film is suddenly heated and suddenly cooled to form an amorphous phase so that the reflectance of light changes to record data.
The pickup controller 6 controls the position of the pickup so that data is properly recorded along a guide groove preformed on the optical disc S. More specifically, the pickup 4 radiates a laser beam to the guide groove. Then, the amount of deviation of the optical axis of the laser beam from the center of the groove is detected from the reflection of the laser beam. The position of the pickup 4 is corrected in accordance with the deviation amount so that the laser beam properly traces the guide groove.
The buffer RAM 7 is connected to the CD-ROM encoder 1 to temporarily store the data provided to the CD-ROM encoder 1 from the host computer. In the CD-ROM encoder 1, an error detection code EDC and an error correction code ECC are calculated for each block. Since the calculated codes are added to a single block of data, at least one block of CD-ROM data is required to perform processing with the CD-ROM encoder 1. Thus, the buffer RAM 7 is provided to store a single block of CD-ROM data required for processing.
The control microcomputer 8 controls the CD-ROM encoder 1, the digital signal processing circuit 2, the analog signal processing circuit 3, and the pickup controller 6 in accordance with a control program. The control program is prestored in a non-volatile memory (not shown), such as an externally connected flash memory, and read when required in response to command data provide from the host computer.
In the CD-R/CD-RW system 50, as a result in the progress of integration technology, the control microcomputer 8 and the CD-ROM encoder 1 are formed on the same (single) semiconductor substrate, and a CD-ROM encoder IC incorporating a control microcomputer is manufactured. This reduces the number of parts in the CD-R/CD-RW system 50 and reduces the size of the entire system. However, the nonvolatile memory, which was arranged adjacent to the control microcomputer 8, is externally connected to the CD-ROM encoder IC due to the incorporation of the control microcomputer 8. This increases the total number of pins of the CD-ROM encoder IC. As a result, the chip area of the CD-ROM encoder IC increases. This is an obstacle when further reducing the size of the entire system.
Regardless of the integrated level of the internal circuits, the chip area of a semiconductor integrated device may be determined by the number of pins arranged along the periphery of an IC chip. The recent progress in integration technology has mage this tendency stronger. The tendency may also be seen in the CD-ROM encoder IC (data processor) that incorporates the control microcomputer. For example, in a CD-ROM encoder IC chip having 256 pins, if the IC chip is square, 64 pins are formed on each side of the chip. Since a certain length is required for each side of the IC chip, there is a limit to reducing the side length of the chip even if the integration level of internal circuits is increased and the chip area is reduced. Thus, to further reduce the chip area, the total number of pins arranged on the chip must be decreased.